Multilayer heat-shrink plastics material film

ABSTRACT

The invention provides a multilayer heat-shrink film, comprising a central first layer made up of a first composition comprising at least one polyolefin; intermediate second layers made up of a second composition and covering respective faces of the first layer, the second composition comprising a styrene-based resin; and outer third layers made up of a third composition and covering respective ones of the intermediate second layers, the third composition comprising at least one polyester.

CROSS REFERENCE TO RELATED APPLICATIONS

Applicant hereby claims foreign priority benefits under U.S.C. §119 fromFrench Patent Application No. 12 60271 filed on Oct. 26, 2012, thecontents of which are incorporated by reference herein.

TECHNICAL FIELD

The invention relates to a multilayer heat-shrink plastics materialfilm, preferably obtained by coextrusion and presenting low density, andmore particularly a film adapted to making heat-shrink sleeves forcovering articles made of polyethylene terephthalate (PET), such asbottles.

BACKGROUND OF THE INVENTION

Document EP 2 008 811 discloses a heat-shrink plastics material filmcomprising a central layer mainly containing polyolefin resin, outerlayers containing a polyester resin, and intermediate layers including apolyethylene resin including a glycidyl methacrylate compound.

OBJECT OF THE INVENTION

One object of the invention is to provide a film with reinforcedcohesion between the layers.

Another object of the invention is to provide a film having a spectrumin the near infrared that is adapted, e.g. either to be close to that ofthe PET container covered with such a film, or else on the contrary tobe specific so as to enable the sleeve made using such a film to bedistinguished from other sleeves.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a multilayer heat-shrink film, comprising:

-   -   a central first layer made up of a first composition comprising        at least one polyolefin;    -   intermediate second layers made up of a second composition and        covering respective faces of the first layer, the second        composition comprising a styrene-based resin; and    -   outer third layers made up of a third composition and covering        respective ones of the intermediate second layers, the third        composition comprising at least one polyester.

This thus produces a multilayer film comprising the following respectivelayers stacked one on another:

-   -   an outer third layer;    -   an intermediate second layer;    -   a central first layer;    -   an intermediate second layer; and    -   an outer third layer.

The use of a styrene-based resin for the intermediate layers serves toreinforce the cohesion between the layers. In particular, when a sleeveis made from the film of the invention, the styrene-based resin for theintermediate layers makes it possible to avoid the layers separatingfrom one another during heat-shrinking of the sleeve on a bottle or onsome other medium.

The materials used make it possible to obtain a low density film capableof ensuring that sleeves made from such a film float.

It is thus easy to recycle such sleeves. When recycling PET bottles,bottles carrying their sleeves are ground up and then immersed in apool. The PET pellets from the bottles then sink, while the pelletscoming from the sleeves float on the surface of the pool. It is thuseasy to separate the PET from the sleeves and avoid pellets coming fromthe sleeves remaining with the PET pellets in the remainder of therecycling cycle, given that the pellets from the sleeves run the risk ofdegrading the recycling of PET pellets.

The materials used are selected so that the film preferably presentsspecific gravity of less than 1.

Preferably, the film is made up solely of the central first layer, theintermediate second layers, and the outer third layers.

In a preferred embodiment of the invention, the resin of the secondcomposition comprises at least one thermoplastic elastomer based on astyrene-block copolymer, in particular a firstpolystyrene-polybutadiene-polystyrene block copolymer.

Preferably, the polystyrene-polybutadiene-polystyrene first blockcopolymer comprises 70% by weight styrene units relative to the totalweight of the first block copolymer.

By way of example, the first copolymer is Styroflex 2G66 (registeredtrademark).

Preferably, the resin of the second composition comprises, in additionto:

-   -   a) the first polystyrene-polybutadiene-polystyrene block        copolymer having 70% by weight of styrene units relative to the        total weight of the first block copolymer;    -   one or more ingredients selected from:    -   b) a second polystyrene-polybutadiene-polystyrene block        copolymer having less than 70% by weight of styrene units        relative to the total weight of the second block copolymer; and    -   c) a polystyrene.

Under such circumstances, the compounds a), b), c) are in the resin atrespective weight proportions lying in the respective ranges a): [30%,80%]; b): [0%, 70%]; c): [0%, 30%]; the sum of the three proportionsbeing equal to 100%.

In a particular aspect of the invention, the first composition comprisesone or more polyolefins selected from:

-   -   d) a first linear low-density polyethylene;    -   e) a second linear low-density polyethylene;    -   f) a high-density polyethylene;    -   g) a metallocene-catalyzed linear low-density polyethylene; and    -   h) a propropylene.

Advantageously, the polyolefins d), e), f), g), and h) are then presentin the first composition at respective weight proportions lying in thefollowing respective ranges d): [20%, 40%]; e): [30%, 60%]; f): [20%,40%]; g): [30%, 70%]; and h): [0%, 40%]; the sum of the weightproportions being equal to 100%.

In yet another particular aspect of the invention, the third compositioncomprises one or more compounds selected from:

-   -   i) a 1,4 cyclohexanedimethanol modified polyethylene        terephthalate;    -   j) a polyester or a copolyester having a low glass transition        temperature;    -   k) a neopentyl glycol modified polyethylene terephthalate; and    -   l) a crystallizable polyester.

Preferably, the compounds i), j), k), and l) are then present in thethird composition in respective weight proportions lying in thefollowing respective ranges i): [0%, 99%]; j): [0%, 40%]; k): [0%, 99%];and l): [0%, 20%]; the sum of the weight proportions being equal to100%.

Advantageously, the compound j) is a diethylene glycol modifiedpolyethylene terephthalate.

Advantageously, the compound l) is polyethylene terephthalate.

Advantageously, the third composition further comprises at least oneslip agent such as a silicate or a mixture of talc and a fatty acidamide or a mixture of a plurality of fatty acid amides.

Preferably, the central first layer has thickness lying in the range 55%to 70% of the total thickness of the film, the intermediate secondlayers together have thickness lying in the range 15% to 30% of thetotal thickness of the film, and the outer third layers together havethickness lying in the range 15% to 30% of the total thickness of thefilm.

In another particular aspect of the invention, each of the outer thirdlayers comprises a compound having an emission spectrum in the nearinfrared that is centered on a wavelength lying in the range 1400nanometers (nm) to 1900 nm.

Advantageously, the compound enables a sleeve made from such a film tobe easily distinguished from sleeves made using other films. Whensorting bottles optically, the near infrared spectrum of a sleeve madefrom such a film is necessarily different from the spectrum of sleevesmade using other films, such that the presence of the sleeve does notinterfere with sorting PET bottles.

Advantageously, the compound is a varnish covering the free surfaces ofthe two outer third layers.

Alternatively, the compound is incorporated in the third composition insuch a manner that the two outer third layers have an emission spectrumin the near infrared centered on a wavelength lying in the range 1400 nmto 1900 nm. Advantageously, the compound comprises polyethyleneterephthalate. Also advantageously, the compound comprises a glycolmodified polyester or an acid modified polyester.

In a variant, the compound is selected to give the film a near infraredspectrum that is close to that of the PET container covered using such afilm. While sorting bottles optically, the near infrared spectrum of asleeve made from such a film does not interfere with the near infraredspectrum of PET bottles covered in said film, such that the presence ofthe sleeve does not impede sorting PET bottles.

While the present invention has been illustrated and described withrespect to a particular embodiment thereof, it should be appreciated bythose of ordinary skill in the art that various modifications to thisinvention may be made without departing from the spirit and scope of thepresent.

What is claimed is:
 1. A multilayer heat-shrink film, characterized inthat it comprises: a central first layer made up of a first compositioncomprising at least one polyolefin; intermediate second layers made upof a second composition and covering respective faces of the firstlayer, the second composition comprising a styrene-based resin; andouter third layers made up of a third composition and coveringrespective ones of the intermediate second layers, the third compositioncomprising at least one polyester.
 2. The film according to claim 1,wherein the resin of the second composition comprises at least onethermoplastic elastomer based on a styrene-block copolymer.
 3. The filmaccording to claim 2, wherein the styrene-block copolymer is apolystyrene-polybutadiene-polystyrene block copolymer.
 4. The filmaccording to claim 3, wherein the polystyrene-polybutadiene-polystyreneblock copolymer comprises 70% by weight styrene units relative to thetotal weight of the block copolymer.
 5. The film according to claim 4,wherein the resin of the second composition comprises, in addition tothe following compound: a) the polystyrene-polybutadiene-polystyreneblock copolymer, as first block copolymer, having 70% by weight ofstyrene units relative to the total weight of the first block copolymer;at least one of the compounds selected from: b) a secondpolystyrene-polybutadiene-polystyrene block copolymer having less than70% by weight of styrene units relative to the total weight of thesecond block copolymer; and c) a polystyrene.
 6. The film according toclaim 5, wherein the compounds a), b), c) are in the resin at respectiveweight proportions lying in the following respective ranges a): [30%,80%]; b): [0%, 70%]; c): [0%, 30%]; the sum of the three proportionsbeing equal to 100%.
 7. The film according to claim 1, wherein the firstcomposition comprises one or more polyolefins selected from: d) a firstlinear low-density polyethylene; e) a second linear low-densitypolyethylene; f) a high-density polyethylene; g) a metallocene-catalyzedlinear low-density polyethylene; and h) a propropylene.
 8. The filmaccording to claim 7, wherein the polyolefins d), e), f), g), and h) arepresent in the first composition at respective weight proportions lyingin the following respective ranges d): [20%, 40%]; e): [30%, 60%]; f):[20%, 40%]; g): [30%, 70%]; and h): [0%, 40%]; the sum of the weightproportions being equal to 100%.
 9. The film according to claim 1,wherein the third composition comprises one or more compounds selectedfrom: i) a 1,4 cyclohexanedimethanol modified polyethyleneterephthalate; j) a polyester or a copolyester having a low glasstransition temperature; k) a neopentyl glycol modified polyethyleneterephthalate; and l) a crystallizable polyester.
 10. The film accordingto claim 9, wherein the compounds i), j), k), and l) are present in thethird composition in respective weight proportions lying in thefollowing respective ranges i): [0%, 99%]; j): [0%, 40%]; k): [0%, 99%];and l): [0%, 20%]; the sum of the weight proportions being equal to100%.
 11. The film according to claim 9, wherein the compound j) is adiethylene glycol modified polyethylene terephthalate.
 12. The filmaccording to claim 9, wherein the compound l) is polyethyleneterephthalate.
 13. The film according to claim 9, wherein the thirdcomposition further comprises at least one slip agent such as a silicateor a mixture of talc and a fatty acid amide or a mixture of a pluralityof fatty acid amides.
 14. The film according to claim 1, wherein thecentral first layer has thickness lying in the range 55% to 70% of thetotal thickness of the film, the intermediate second layers togetherhave thickness lying in the range 15% to 30% of the total thickness ofthe film, and the outer third layers together have thickness lying inthe range 15% to 30% of the total thickness of the film.
 15. The filmaccording to claim 1, wherein each of the outer third layers comprises acompound having an emission spectrum in the near infrared that iscentered on a wavelength lying in the range 1400 to 1900 nanometers. 16.The film according to claim 15, wherein the compound is a varnishcovering the free surfaces of the two outer third layers.
 17. The filmaccording to claim 15, wherein the compound is incorporated in the thirdcomposition in such a manner that the two outer third layers have anemission spectrum in the near infrared centered on a wavelength lying inthe range 1400 to 1900 nanometers.
 18. The film according to claim 17,wherein the compound comprises polyethylene terephthalate.
 19. The filmaccording to claim 17, wherein the compound comprises a glycol modifiedpolyester or an acid modified polyester.